Conventionally, in laboratories and production sites where measurement devices such as electronic balances are used, monitoring (recording over time) of installation environmental conditions (temperature, humidity, air pressure, etc.) that affect the performance of the measurement devices in parallel with measured values has been commonly performed. In this case, due to the demand for freedom of data processing in data analysis, data loggers capable of digitally recording measurement data and installation environmental data have been often used. For example, as regards the measurement data, a digital measurement data logger that receives measurement data from a measurement device, digitally records numerical values, and enables output of the same to a personal computer (hereinafter, a PC) via a USB terminal (Patent Literature 1) has been provided, and as regards the installation environmental data, a digital environmental data logger capable of receiving environmental data from respective environmental measuring instruments, digitally recording numerical values, and displaying such environmental data on its own display section (Patent Literature 2) etc., has been provided.